1. Field of the Invention
The present invention relates to an ultrasonic method and an ultrasonic device for characterizing a medium.
The present invention applies in particular to the characterization of solid media constituting objects for which it is a question of ascertaining the nature, composition, degree of homogeneity, state, a dimension etc., in particular by comparison with results established previously for known media.
In particular it may be a matter of detecting the condition of a mechanical component by non-destructive means. More particularly, it may be a question of examining the condition of a human or animal bone, in particular the state of the cortical layer of the bone, for example to ascertain the stage of development of a bone in a child, the condition of a bone in the case of certain disabilities affecting the skeleton, or for detecting bone pathologies such as osteoporosis and if necessary evaluating the severity of the pathology detected.
2. Description of Related Art
Ultrasonic methods offer numerous advantages relative to radiographic methods, which require expensive equipment and a suitable environment, which have undesirable side effects and for which the frequency of application on the same individual must be limited.
Methods of characterization are known that consist of applying ultrasonic excitation at an emission site and detecting, at several successive receiving sites, the arrival of the first signal generated by said excitation, then calculating the velocity of propagation of this first signal. The method can be implemented by applying a probe on the external surface of the patient's body. FR 2 839 877 teaches a method and a device that eliminate the influence of a possibly variable thickness of soft tissues (skin, muscle) between the probe and the bone to be investigated. In the cortical layer of a bone, the velocity of the first signal varies as a function of parameters such as the thickness of the cortical layer, the presence of osteoporosis etc. Just measuring the velocity of the first signal therefore does not always permit discrimination of different symptoms.